Control element for the flushing device in hydraulic gears



O. HEERDT Feb. 2,. 1937.

CONTROL ELEMENT FOR THE FLUSHING DEVICE IN HYDRAULIC GEARS Filed Dec. 24, 1935 lnvenfor firm 5 m4 Patented Feb. 2,- 1937 UNITED STATES PATENT OFFICE aosasce CONTROL ELEMENT FOR; TiiE FLUSHING DEVICE IN HYDRAULIC'GEARS Otto Heerdt, Leipzig, Germany,

Application December 24, 1935, Serial No; 56,000 In Germany March 5, 1935 3 Claims.

My invention relates to a reversing valve and more particularly to a reversing valve for use in a so-called makeup system of a reversible hya pump connected with each other by circuit I lines, whereby the direction 01 rotation of said motor and pump may be reversed. Depending on the direction of rotation of the motor and pump, either one or the other of the circuit lines from the reservoir into the suction line of the 20 circuit, and excess fluid flows from the suction line into the reservoir. Due to the fact, that in reversible hydraulic transmissions the suction line may become a pressure line and vice versa, a reversing valve must be provided in the piping 25 system of the make-up system, which assures a correct working of the latter and permits a;

flowing of the make-up fluid through the circuit line, which at the moment forms the suction line. The above mentioned German patent 30 to Thoma discloses such a reversing valve, which acts automaticallyin dependence on ,the pressure in the lines of the circuit and consists of an integral member provided with two valve bodies.

Such a valve, however, acts only at a comparatively high speed of flow in the pressure line.

One object of my invention, is to provide a reversing valve, which acts at a comparatively low speed of flow in the pressure line.

In order to carry out my invention into prac-' tice, the reversing element consists, as usual,-

simple construction, it consists in that every valve stem is constructed as a cylinder in which -a control piston moves which is influenced by the pressure oil.

I accomplish the purpose of my invention by means of a reversing valve one embodiment of which is described in the following specification 5 and illustratively exemplified in the accompanying drawing, which shows a longitudinal sectional view of'the reversing valve and a diagrammatical view of the hydraulic transmission and the make-up system connected thereto.

\ vReferring to the drawing, I denotes a housing of the valve, in which two inlets 2 and 3 and at the middle between them a discharge conduit 4 are arranged. Between the admission conduits for the oil the discharge conduit valves 5 and G are arranged, the stems and'8 of which are cylindrically bored and accommodate each a control piston 9, I0 respectively. The valves 5 and 6 have each an extension II, I2 respectively with a bore I3, I4 respectively so that the end faces of the control pistons on the valve bodies can come under the pressure of the oil standing in the conduits 2 and 3. The valves are further influenced-by springs I5.

The; reversible hydraulic transmission consists o the hydraulic pump I00 and motor ml, which at connected with each other by the circuit lines Illli'andgills and may work in both directions of rotation. Line I02 is connected to the inlet 2 of the reversing valve by the conduit I04, while line I03 is connected to the inlet 3 by the conduit .The make-up system contains the' auxiliary pump I05 and the reservoir I01 in addition to the reversing valve described. The discharging end of the auxiliary pump I06 is connected to a 'pipe I08, which branches into two pipes I09 and'IIO provided with check-valves III and H2 respectively. The branching pipe I09 enters into the circuit line I02, the branching pipe IIO enters 40 into the circuit line I03, The reservoir I0! is connected to the outlet 4 of the reversing valve byapipe II3.

The operation of the'device is as follows: Assuming, pump I00 and motor IOI rotate in clockwise direction, so that the line I02 is the suction line and line I03 is the pressure line. Under said conditions, the valve 6 will be closed by the pressure existing in the line I03 and conduit I05. The oil pressure acts at thesame time through a channel I4 upon the control piston lo and shifts the same to the left, the control piston 9 and the valve 5 being moved thereby, so that valve 5 is opened. The make-up 11 livered by the auxiliary pump I06 through the pipe I09 into the suction line I02 and partly flowing therefrom through the conduit I04 into the inlet 2 of the reversing valve can therefore flow through the channels of stem I into the conduit 4. If the direction of rotation'of the gear is changed into anti-clockwise direction, the line I02 becomes a suction line, and the liquid in the inlet 2 comes under pressure, so that the valve 5 is closed, the spring acting to close the valve. The control pistons 9 and I0 are moved in accordance with the valve stroke. As, however, the oil pressure continues then to act upon the control piston 9 through the bore I3 both pistons are shifted and the piston I 0 opens the valve 6 against the action of spring I5. If the reversing valve is in this right-hand position, the auxiliary pump I06 delivers the make-up oil through the pipe H0 into the suction line I03, from where it flows partly through the conduit I05, reversing valve, outlet 4 and pipe II3 into the reservoir.

In this manner it becomes possible to effect a reliable reversing even at a relatively slow speed of flow, as the valves are not rigidly connected the one with the other, but a control arrangement is interposed between them. The details may be otherwise constructed than described.

I claim:

1; In a reversing valve for use in a line connecting the reservoir of a make-up system to the circuit lines of a reversible hydraulic transmission, the combinationof a housing, an inlet in said housing adapted to be connected to one of said circuit lines, another inlet in said housing adapted to be connected to the other circuit line,-

an outlet in said housing adapted to be connected to the line leading to said reservoir, a bore in said housing communicating said outlet and inlets with each other, a valve arranged in said bore between one of said inlets and said outlet, another valve disposed in said bore between the other inlet and said outlet, said valves being movable independently of each other, and automatic hydraulic controlling means adapted to be actuated by the pressure in the circuit line carrying the liquid under high pressure and to open the valve arranged between the circuit line carrying the liquid under low, pressure and said outlet.

2. In a reversing valve for use in a-line connecting the reservoir, of a make-up system to the circuit lines of a reversible hydraulic transmission, the combination of a housing, an inlet in said housing adapted to be connected to one of said circuit lines, another inlet in said housing adapted to be connected to the other circuit line, an outlet in said housing adapted to be connected to the line leading to said reservoir, a bore in said housing communicating said outlet and inlets with each other, a valve arranged in said bore between one of said inlets and said outlet, another valve disposed in said bore between the other inlet and said outlet, each of said valves being provided with a stem slidably arranged in said bore, each stem having channels for the passage of the fluid and a center hole communicating with said inlet through a conduit, said valves being separated from each other and being movable independently of each other, and automatic hydraulic controlling means adapted to be actuated by the pressure in the circuit line carrying the liquid under high pressure and to open the valve arranged between the circuit line carrying the liquid under low pressure and said outlet, said hydraulic controlling means comprising two pistons, each of said pistons being movably arranged in said center hole of the valve stem, adjacent ends of said pistons abutting against each other, the free end of each of said pistons facing'said abutment of the valve body.

3. In a reversing valve as claimed in claim 2 the arrangement of springs tending to close the conduit and being adapted to bear against an 

